In the context of mailpiece delivery, a self-mailer is a term used for identifying mailpieces which employ some portion of its content information or material to form a finished mailpiece, i.e., a mailpiece ready for delivery. In addition to certain efficiencies gained from the dual use of paper stock, i.e., as both envelope and content material, self-mailers mitigate the potential for disassociation of content material from the mailing envelope, i.e., preventing mail from being delivered to an incorrect address.
In the simplest form, a self-mailer may include a single sheet of paper having printed communications or text on one side thereof and a mailing address on the other. The sheet is then folded and sealed to conceal the printed communications while causing the mailing address to remain visible. Postage evidence is applied to the face of the mailpiece in preparation for delivery either during the sheet printing operation or after mailpiece fabrication. This example simply shows that a self-mailer generally seeks to make dual use of the content material to both convey information while forming an envelope of a size and shape which is accepted by postal automation equipment. As such, the material and labor cost associated with combining content material with a container or envelope is minimized.
One such self-mailer includes flat mailpieces which are knurled along each edge of a four-sided rectangular mailpiece. These “flats”, as they are frequently called, employ face sheets of paper stock which are oversized relative to the internal content material/sheets such that the peripheral edges thereof extend beyond the edges of the internal sheets on all four sides. The peripheral edges are then deformation bound along the entire length to capture and enclose the content material. Such deformation binding is a process wherein, following plastic deformation of the sheets, the elastic properties thereof develop mechanical forces at or along the interface, which forces are sufficient to bind the sheets together. Alternatively, or additionally, deformation binding may also be viewed as a process wherein the individual fibers of paper stock, upon the application of sufficient pressure/force, interleave or “hook” to form a mechanical interlock. As such, the content material and face sheets may be produced at a single workstation, stacked together and bound without the need for other handling processes i.e., such as folding of the content material or insertion of the content material into an envelope. Furthermore, and, perhaps more importantly, a self-mailer eliminates the requirement for consumable materials such as glue, staples or clips to form the enclosure or bind the edges.
Notwithstanding the potential benefits achievable by deformation binding, drawbacks principally to the binding efficiency or speed offer some explanation for its lack of widespread acceptance and use. For example, and referring to FIG. 1, the knurling wheels 100 of the prior art bind each pair of parallel edges 102a, 102b of a rectangular mailpiece 104 in a two step binding operation. More specifically, in a first operation, pairs of knurling wheels 100a deformation bind the edges 102a of the mailpiece 104 as the mailpiece travels in a first direction, indicated by arrow 106. In a second operation, pairs of knurling wheels 100b deformation bind the orthogonal edges 102b of the mailpiece 104 as the mailpiece travels in a second direction, indicated by arrow 108. The mailpiece 104 must come to a stop between each of the two binding operations and change direction, i.e., the second direction 108 is orthogonal relative to the first direction 106.
While the two step binding sequence described above may be suitable for fabricating mailpieces in small quantities, this manufacturing approach is less acceptable for fabricating large quantities of mailpieces. That is, the orthogonal re-direction of the mailpiece slows fabrication sufficiently to render the process inappropriate for high-volume, high speed mailpiece fabrication.
Furthermore, the registration and alignment of content material requires exact placement to avoid deformation binding of the internal sheets in combination with the face sheets as the peripheral edges are bound. To avoid such difficulties, the face sheets are further enlarged, or content material undersized, to accommodate errors in the relative placement of the internal sheets. Notwithstanding such precautionary measures, shifting of the internal content material remains problematic until at least a portion of the stacked sheet material is deformation bound.
Additionally, and referring to FIG. 2a, the knurling wheels of the prior art produce a knurl pattern KP which tends to weaken the corners 110 of the bound mailpiece 104. That is, inasmuch as the knurling wheels deformation bind the mailpiece edges 102a, 102b along the entire edge, each linear pass causes an overlap in the corners thereby weakening the mailpiece 104, i.e., reducing its structural integrity, at the corners 110 thereof. While the binding operation could be controlled to avoid binding redundancy in the corner regions, i.e., by controlling the gap between each pair of knurling wheels at appropriate points along the linear travel, such control motion would require additional mechanical complexity and further reduce the speed of operation. With respect to the latter, it will be appreciated that the speed and complexity of operation will be adversely impacted by any non-continuous motion of the knurling wheels or transport deck.
Finally, while self-mailers do not necessarily require the use of consumable materials, such mailers typically employ prefabricated paper stock or specialty forms. That is, such mailers oftentimes incorporate unique glue lines, or windows cutout to facilitate fabrication or printing. As a result, their unique design does not facilitate or accommodate the use of conventional paper stock, i.e., common size and paper thickness/consistency. Consequently, while certain mailpiece fabrication costs are reduced, others, i.e., such as the prefabricated paper stock used in its fabrication, are greatly increased.
A need, therefore, exists for an efficient, high speed apparatus for fabricating packages having multiple sheets of content material which minimizes mechanical complexities, eliminates the use of consumable materials and facilitates fabrication using conventional paper stock.